System to prevent freezing of heating units such as boilers

ABSTRACT

A control system to prevent freezing of heating units, such as boilers, particularly those which may be outdoors, such as on a rooftop. A drain valve is provided to automatically drain the water from the unit in the event of power failure which would prevent heating of the water, or in the event of the occurrence of a low temperature of the water approaching freezing, or both. The system may also include a valve which closes in response to one or both of these conditions to prevent admission of water to the unit. The drain valve embodies a time delay feature so as to not respond to power failures of minimum predetermined duration.

United Sttes Block et a1.

atttt [1 1 [451 May 28, 1974 SYSTEM TO PREVENT FREEZING 0F HEATING UNITSSUCH AS BOILERS [73] Assignee: Raypak, 1nc., Westlake Village,

Calif.

22 Filed: June 22,1972

211 App]. No.: 265,125

3,446,226 5/1969 Canterbury I: 137/62 FOREIGN PATENTS OR APPLlCATlONS1,137,405 12/1968 Great Britain 137/62 Primary Examiner-Alan CohanAssistant Examiner-Richard Gerard Attorney, Agent, or Firm-Herzig &Walsh [5 7 ABSTRACT A control system to prevent freezing of heatingunits, such as boilers, particularly those which may be outdoors, suchas on a rooftop. A drain valve is provided to automatically drain thewater from the unit in the event of power failure which would preventheating of the water, or in the event of the occurrence of a lowtemperature of the water approaching freezing, or both. The system mayalso include a valve which closes in response to one or both of theseconditions to prevent admission of water to the unit. The drain valveembodies a time delay feature so as to not respond to power failures ofminimum predetermined duration.

1 Claim, 3 Drawing Figures SYSTEM TO PREVENT FREEZING OF HEATING UNITSSUCH AS BOILERS SUMMARY OF THE INVENTION The invention is an automaticcontrol system adapted for use with heating units, such as boilers andparticularly boilers which are situated outdoors, such as for example ona rooftop. Such heating units or boilers are particularly subject to thehazard of damage resulting from freezing of the liquid in the boilerwhich typically would be water. Freezing could result from inoperationof the boiler caused by various occurrences, such as power failure,particularly; interruption of gas or fuel supply; safety shutdown due topilot outage; or other comparable reasons including inadequate orinsufficient water flow; etc.

The primary object of the invention is to provide an automatic controlmeans to protect the boiler from freezing from any of the aboveennumerated contigencies.

In a typical type of installation, the heating unit or boiler may be onethat is gas fired, although the invention is adaptable in any type ofsystem wherein it is desired to protect the heating unit against thehazard of damage from freezing. The invention is described in detailherein as adapted in a gas fired water heating system wherein the boiler(heating unit) is installed on a rooftop.

In a preferred exemplary form of the invention, an automatic normallyclosed (The word normal herein means normal or ordinary operation of thesystem rather than referring to a valve position as related to its beingenergized or de-energized.) valve is provided to automatically open anddrain the boiler in the event of power failure. The valve may also becaused to open in response to the occurrence of a low temperature of thewater in the boiler approaching freezing. The valve can be maderesponsive to both conditions. Additional valve means may be optionallyprovided, that is, a normally open valve means controlling the supply ofwater to the boiler which closes when one or both of said conditionsoccur. In some installations, it is desirable and more economical to notprovide the normally open valve, but in the event of occurrence of thesaid condition or conditions, water is allowed to be continued to besupplied to flow through the boiler and to drain therefrom while thecondition prevails. Preferably, a boiler vent valve is provided which isopened in response to the condition or conditions to insure that thedrain will take place.

A further object is to provide a control system for protection of aboiler as referred to wherein a normally closed valve is provided toautomatically open and drain the boiler in the event of a power failurecondition and/or a low temperature in the boiler or other conditionindicative of the hazard that there might be freezing of the boiler.

A further object is to provide a system as in the foregoing objectproviding further, a normally open valve which closes to prevent flow ofwater to the boiler in the event of occurrence of the condition.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and additionaladvantages of the invention will become apparent from the followingdetailed description and annexed drawings, wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of thedrawings, a typical rooftop type installation is illustrated. The rooflevel is designated at 10 and the boiler is designated at 12. Theheating unit which is typically referred to in the art as a boiler maybe of a conventional type fired by gas such as the one shown in US. Pat.No. 3,575,157.

Numeral M indicates a line or pipe connected to a city water supplywhich connects to pipes l6, l7, and 19 and to the boiler. In pipe 22,there is provided an expansion tank 18. The discharge line from theboiler is designated at 22. These lines are connected to a typicalheating system which may be a space heating system as designated at 24.

In line 14-16 there is provided a normally open valve 30 which may be asolenoid type valve that controls supply of water to the system.

Numeral 34 designates a branch line connected to return line 17 havingin it a normally closed bellows operated valve 35. This valve is of atime delay type which although it is normally closed, in the event of apower failure it will automatically open after a predetermined timedelay of an established number of seconds. The valve is of this type sothat in the event of momentary power failures of a few seconds, it willnot open undesirably. As will be noted, drain valve 35 has a valvemember 36 connected to bellows 37. Surrounding the bellows is anelectrical heating coil 39. Whenever this coil is energized, the fluidin the bellows expands seating valve member 36 and thus closing thevalve. Whenever coil 39 is deenergized, the fluid in bellows 37 willcool and contract, and in a predetermined number of seconds will openthe valve.

Numerals 38 and 40 designate flow switches which may be of aconventional type and may be connected in the control system for theheating apparatus of the boiler which may involve a typical gas controlvalve, a safety valve, a pilot operated switch, etc. as is already wellknown in the art. It is therefore not shown in detail herein.

Numeral 44 designates a temperature actuated switch actuatable inresponse to thermostatic bulb 46 and tube 48 as shown responsive totemperature of water in the lower part of the boiler.

Numeral 50 designates the drain linefrom valve 35 arranged to drain intoa funnel 52 and into the end of a line 54. Line 50 is provided with anorifice 56 ahead of which is line 58 connected to pressure responsivediaphragm switch 60. This switch is connected in a battery poweredcircuit controlling an alarm 64 which may be of various types, such asvisual or audible. Such alarm would be located at an appropriate controlcenter or station to advise supervisory personnel that valve 36 is openand the boiler is draining.

Numeral 62 designates a vent valve connected to the boiler in such a wayso as to be able to vent its water system to the atmosphere to insurethat the boiler would drain in the event that valve 35 opens.

The system as shown is electrically controlled. Numeral 70 designates atransformer having a primary winding 71 and secondary winding 72. Itwill be noted that secondary winding is connected to thermostatic switch44 which controls parallel circuits for all three valves.

In the event of power failure or opening of switch 44 in response to lowtemperature, valve 30 closes (deenergized); valve 62 opens(deenergized); coil 39 is deenergized and valve 35 opens.

As pointed out in the foregoing, the basic system itself may be ofvarious alternative types embodying various different features andarrangements. The expansion tank, for example, might be below the levelof the rooftop. The system might be one having an accumulator or storagetank or one without such a tank as in known in the art as for example inthe patent referred to above. The heated water distribution system maybe connected directly to the boiler or on the other hand, it may beconnected to the accumulator or storage tank. FIG. 3 shows such a systemhaving an accumulator or storage tank 76 having connections 77 and 78 toa water distribution system. Pipe 22 connects to tank 76, and pipe 81connects the tank to pipe 16.

FIG. 2 shows a possible alternative or modification wherein drain valve35 is a mechanically operated type responsive to a thermostatic bulb 84adjacent discharge line 22 and connected to the valve by tube 85. Thethermostat normally will maintain the valve closed and at apredetermined relatively low temperature indicating' that freezing ofthe water has become a possible hazard, the fluid in the bulb willcontract sufficiently to cause the drain valve to open allowing theboiler to drain. If desired, a similar mechanically actuated normallyopen thermostatic valve can be provided to control the flow of water tothe boiler. In a system as shown in FIG. 2, power failure protection canbe embodied also if'desired.

Fromthe foregoing, those skilled in the art will readily understand thenature and operation of the system of the invention. As pointed out, thesystem may or may not embody the normally open inlet control valve, andthe controls can be responsive to power failure or temperature or bothas shown. In some hydronics systems which are closed systems, it isundesirable to continuously circulate water through the system; andthus, the inlet control valve is used. In some instances, it can bedispensed with, thus reducing expense. In the system as shown, in theevent of power failure, valve 35 will open after a predetermined numberof seconds, the normally open valve 30 will close shutting off flow ofwater to the boiler. The system may be provided without valve 35, inwhich event water from the source will continually flow through theboiler and drain therefrom during the time the hazardous conditionprevails. The temperature of such water will always be such as topreclude freezing of the boiler.

The foregoing disclosure is representative of preferred forms of theinvention and is to be interpreted in an illustrative rather than alimiting sense, the invention to be accorded the full scope of the claimappended hereto.

We claim:

1. A freeze damage prevention system for a heating unit for heatingwater and the like wherein said unit is situated to be subject to damagefrom freezing of the liquid within it, the system comprising: normallyclosed valve means connected to the unit in a position whereby to drainthe liquid from the unit sufficiently to prevent damage from freezing inthe unit; and means controlling said valve means responsive to acondition indicative of possible or imminent freezing of liquid withinthe unit, said responsive means comprising mechanism actuatable inresponse to power failure whereby to cause said normally closed valve toopen, said valve means embodying a time delay mechanism whereby saidvalve means is prevented from opening in response to a power failure ofa predetermined relatively short duration.

1. A freeze damage prevention system for a heating unit for heatingwater and the like wherein said unit is situated to be subject to damagefrom freezing of the liquid within it, the system comprising: normallyclosed valve means connected to the unit in a position whereby to drainthe liquid from the unit sufficiently to prevent damage from freezing inthe unit; and means controlling said valve means responsive to acondition indicative of possible or imminent freezing of liquid withinthe unit, said responsive means comprising mechanism actuatable inresponse to power failure whereby to cause said normally closed valve toopen, said valve means embodying a time delay mechanism whereby saidvalve means is prevented from opening in response to a power failure ofa predetermined relatively short duration.